Some of the most severe forms of pain, particularly chronic inflammatory pain, are resistant to currently available analgesic therapies. Rational design of new pharmacological strategies for treatment of pain will depend on an understanding of the underlying cellular mechanisms. Recent studies in our laboratory and that of Dr. Messing (Project #2) have revealed that the epsilon isoform of protein kinase C (PKCe) plays a central role in hyperalgesia induced by some inflammatory mediators, and we have identified a novel PKCe- dependent mechanism of neuronal plasticity in chronic inflammatory pain, termed 'hyperalgesic priming.' This component of the Program Project proposal is a multidisciplinary investigation of the pivotal role of PKCe in inflammation-induced hyperalgesia, focusing on upstream second messenger pathways that lead to activation of PKCe. (This complements the investigation by Dr. Messing, of mechanisms downstream from PKCe in inflammatory hyperalgesia.) Previous studies of PKCe-mediated hyperalgesia have used simplified models of hyperalgesia based on injection of individual inflammatory mediators. By employing a more generalized model of acute inflammation (induced by carrageenan), the present experiments will make a major step toward our ultimate goal of understanding PKCe-dependent mechanisms in inflammatory pain conditions like those encountered clinically. In Specific Aim 1 we will investigate specific second messenger pathways hypothesized to activate PKCe in acute inflammation-induced hyperalgesia, and possible modulation of PKCe activity by interaction with the actin cytoskeleton. In Specific Aim 2 we will investigate the induction of novel PKCe-dependent signaling mechanisms in chronic hyperalgesia induced by inflammation and stress. An ultimate goal of this research project is to provide a rational basis for the design of novel strategies to treat pain that is intractable to currently available therapies by specifically targeting pathways that control the hyperalgesic actions of PKCe.